openlayers and turfjs(buffer)

Question

I'm using OL v4.3.2 and turfjs. I want to use turf buffer function to create buffer arround a clicked feature based on a radius, but the result is not accurate and the buffer is very smaller than it should be. so anybody can help me? I would be really appreciated.

map.on('singleclick', function (e) {
var coord = e.coordinate;
var pixel = e.pixel;
console.log(coord);
map.forEachFeatureAtPixel(pixel, function (feature, layer) {
    console.log(feature);

    var p= feature.getGeometry().getCoordinates();
    var input_turf = turf.point(p);
    var buffered = turf.buffer(input_turf, 30, 'kilometers');
    var source = new ol.source.Vector();
    var format = new ol.format.GeoJSON();
    var features = format.readFeatures(buffered);
    source.addFeatures(features);
    var bufferd_layer = new ol.layer.Vector({
        source: source
    });
    map.addLayer(bufferd_layer);

},{
    hitTolerance: 15
})

});